Single-atom Ni-N4 sites coordinate dual nonradical oxidation pathways via peroxymonosulfate activation: Computational insights and in situ spectroscopic analyses

In this work, we revealed a dual-pathway nonradical oxidation (NRO) system catalyzed by Ni single atom catalyst (NiN4) accommodated in the carbon nitride substrate. The monatomic Ni coordinated with four N atoms (Ni-N4) is determined as the dynamic catalytic center for peroxymonosulfate (PMS) activation, showing an exceptional specific rate constant of 3.34 min-1 g-2 L-2 (29.7 times that of CN/PMS system) in oxidizing bisphenol A and other refractory organics. In situ Raman, X-ray absorption, and electrochemical analyses as well as theoretical simulations demonstrate that the Ni-N4 sites exhibit strong interaction with PMS benefited from the modulated electronic structures, resulting in nonradical surface-bonding active complexes (NiN4-PMS*) and deuterogenic high-valent Ni(IV)-Oxo species. The dual-pathway NRO process will spontaneously coordinate both electron transfer process via CN matrix and direct electron transfer by Ni(IV)-Oxo for selective organic oxidation with excellent anti-interference ability and adaptability.